THE AMERICAN WELDER Fig. 4 — No blue transparent welding screen complies with the AWS F2.3M:2011 specification. Additional advantages of a transparent screen include better ambient illumination and a reduction of the welder’s sense of confinement. The selection of the protective screen must be based on the transparency needed, with the prerequisite that the screen offers the right level of eye protection for bystanders and other workers near the welding operation. How to Identify a Screen that Complies with the AWS F2.3M:2011 Requirement It is generally not possible for users to evaluate how well one screen performs compared to one that looks similar. This can only be evaluated by performing optical tests with specialized equipment (i.e., spectrophotometer, spectroradiometer, or other spectrallyweighted radiometer). In most cases, the screen’s color and apparent transparency will not indicate if it really stops hazardous radiant energy. The exception is blue screens, which by their very nature transmit blue light radiation at potentially hazardous levels. In addition, the ability of screens of any color to absorb radiant energy can change as the screen ages. In order to help users, select protective screens that comply with the AWS F2.3M:2011 specification and are labeled by their producers — Fig. 3. Why Are Blue Screens Hazardous? Not all screen colors protect equally. Welding arcs emit hazardous levels of blue light that must be filtered to prevent injury. Blue light, which is part of the visible light spectrum, reaches deep into the eye, and its cumulative effect can cause damage to the retina, such as a retinal blind spot. Blue screens appear blue to the human eye because they allow a larger proportion of blue light to reach the eye. Therefore, blue-colored screens cannot significantly filter out blue light, and no blue-transparent welding screen can be compliant with the AWS F2.3M:2011 specification — Fig. 4. AWS F2.3M:2011 requires that welding screens must block all but 0.2% of the blue light emitted by welding arcs. However, in one case an independent laboratory test revealed that one bluetransparent screen permitted more than 25% of the blue light to pass through the screen. To provide adequate protection, the AWS Safety and Health Committee recommends only the use of screens complying with AWS F2.3M:2011. Typically, screens passing the AWS standard are available on the market in red, orange, yellow, green, and bronze. Screens passing the standard will filter hazardous blue light while allowing sufficient light for transparency and safety. Conclusion By looking for the AWS F2.3M:2011 marking, users can take any guesswork out of selecting a screen that will adequately protect bystanders against UV and blue light in the welding environment. Without testing and certification, it is not possible to know if a welding screen provides adequate protection. However, you can be sure that blue-transparent screens do not provide adequate protection and should not be used. 84 WELDING JOURNAL / DECEMBER 2016 WJ For info, go to aws.org/adindex
Welding Journal | December 2016
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